Rotary line trimmers are well known. Such trimmers incorporate a line or core as a cutting edge attached to a line head. A portion of the line extends beyond a central hub of the trimmer. When the central hub is rapidly spun by a motor, the line becomes an effective cutting device for grasses, weeds and other foliage. The line can be made of any number of durable materials such as flexible filament nylon line.
During use, the line is worn away and shortens in length and then must be replenished. There are two basic approaches to replenishing cutting line. In one approach, a supply of flexible line is wound on a spool placed within a hub. The spool and hub for the line head that is rapidly spun by the motor. Line is played out from the hub when the cutting portion of the line becomes too short. Playing the line out is accomplished either manually or automatically. Using a rotating spool has the advantage of keeping a relatively large supply of line on hand for immediate use. Consequently, it is the preferred approach for rotary line trimmers suitable for trimming tougher vegetation or a large area of vegetation. However, spools tend to be relatively complicated mechanisms that are expensive to manufacture and/or difficult to use. Also, each part adds weight and increases the likelihood of failure.
An alternative design, discussed in detail below, places a single length of line within a single head element. The line fits within a channel in the head and is mechanically held in place by a plastic tab. The head is attached to a shaft connected to the trimmer's motor. When the line is worn, the plastic tab can be opened and the line replaced. This design is lighter and less expensive to construct. However, the plastic tab used to retain the line can easily deform or break. Also, dirt and grass can keep the tab from closing. If the tab fails, the entire line can be lost.
Therefore, a need exists for an improved line head for holding a line for a rotary line trimmer. The line head should be simple and inexpensive to construct. The line head should securely hold a single length of line. The method of securing the line should be easily manipulated to remove the line. Moreover, the performance of the device should not be affected by dirt or grass.